In order to conserve energy, an increasing number of homeowners and building contractors are installing insulation throughout their buildings. In many cases the area to be insulated is a cavity in the roof or wall of the building. One type of insulation often used for such cavities is blown-in insulation. Blown-in insulation comprises an insulating material which can be injected into a cavity via air-pressure. A number of different products have been used in the past to fabricate blown-in insulation (i.e. cellulose fiber, fiberglass, rockwool, etc.).
The level of insulation required (the R-value), and therefore the type and amount of insulation used, is dependent on the characteristics of the specific area to be insulated. Insulation manufacturers are constantly searching for low cost materials which exhibit sufficient insulating properties and can be put into a form suitable for blowing into a cavity. Logically, the most inexpensive insulating material which can be used for an application requiring a given R-value is the most desirable.
Fly ash is a coal byproduct which occurs as spherical particles usually ranging in diameter from 0.5 to 100 microns. Depending on the specific makeup of the coal used, when coal is burned, fly ash makes up anywhere from 10 to 85% of the coal ash residue. Up to 20% of fly ash consists of cenospheres, which are lightweight spheres of silicate glass filled with nitrogen and carbon dioxide that float in water. This makes pond disposal of coal ash very difficult as the cenospheres are apt to create a suspended solids problem in the pond. Also, there are significant environmental restrictions and costs associated with other forms of disposal. Therefore, power plants and other producers of fly ash are extremely willing to sell large quantities of fly ash at a relatively modest price (a considerably lower price than an equal volume of standard insulating materials).
Thus, it would be advantageous to use fly ash as an insulating material due to its availability and low cost. In addition, creating insulating material from fly ash provides a productive use for an ordinarily undesirable byproduct.